1. Field of the Invention
The present invention relates to an illumination system and a projection system adopting the same, and more particularly, to an illumination system which can realize a color image without a color wheel, and a projection system adopting the same.
2. Description of the Related Art
Referring to FIG. 1, a conventional projection system includes a light source 100, a first relay lens 102 to condense the light beam emitted from the light source 100, a color wheel 105 to split light beams incident from the first relay lens 102 into R, G and B color light beams, a fly eye lens 107 to make the light beam passing through the color wheel 105 uniform, a second relay lens 110 to condense the light beam passing through the fly eye lens 107, a display device 112 to form a color image from the R, G and B color light beams sequentially input through the color wheel 105, and a projection lens system 115 to make an image formed by the display device 112 proceed toward a screen 118.
A xenon lamp, a metal-halide lamp, or a UHP lamp is used as the light source 100. These lamps emit too much unnecessary infrared and ultraviolet energy. Accordingly, since much heat is generated, a cooling fan is used to cool the system. However, the cooling fan also acts as a noise source. Also, since the spectrum of the lamp light source is widely distributed across many wavelengths, due to a narrow color gamut, the selection of color is limited, color purity is inferior, and the life span is short. Thus, long-term use of the lamp is not possible.
In the conventional projection system, to realize a color image, the color wheel 105 is rotated by driving a motor (not shown) at a high speed so that R, G and B color light beams are sequentially illuminated onto the display device 112. R, G and B color filters are equally arranged on the entire surface of the color wheel 105. The color wheel 105 rotates three turns for each image. The three colors are sequentially used, but only one color is used for each rotation, thus, ⅔ of the light is lost. Also, more light is lost at a boundary portion between neighboring color filters.
Furthermore, since the color wheel 105 rotates at a high speed, noise is generated. Also, the mechanical movement of the driving motor has an adverse effect on stability. Further, due to mechanical limitations of the driving motor, it is difficult to obtain a speed over certain ranges and a color breakup phenomenon occurs. Also, since the price of the color wheel is very high, the manufacturing cost increases.